Nitro-containing epoxy compounds



United States Patent 3,335,155 NITRO-CONTAINING EPOXY COMPOUNDS GustaveB. Linden, Short Hills, N.J., and Ralph E. Meyer and Clinton R.Vanneman, Sacramento, Calif., assignnors to Aerojet-General Corporation,Azusa, Califi, a corporation of Ohio No Drawing. Original applicationJune 2, 1964, Ser. No. 372,122.. Divided and this application Oct. 12,1965, Ser. No. 516,804

4 Claims. (Cl. 260-348) This application is a division of Ser. No.372,122, filed June 2, 1964.

This invention pertains to several types of novel epoxy compoundscontaining in the molecular structure one or more nitro groups, and totheir method of synthesis.

Nitro-conta-ining diols have been used in the preparation of binders forsolid rocket propellants. While these known binders do possess a fairlyhigh specific impulse, their mechanical and chemical properties stillleave room for considerable improvement. In the commercial polyurethanefield, it is known that the use of polyalkylene ether polyols improvesthe properties of polymers produced from them. The polyurethanes frompolyalkylene ether polyols are disclosed in US. Patent No. 2,948,691,issued August 9, 1960. However, the advantages resultant from polyetherlinkages in the polyurethane chain have not heretofor been available inthe high energy polymer binder field because of the lack of a suitablemonomer from which could he obtained high-molecular weight,nitrocontaining polyalkylene ether polyols. According to our invention,there now has been discovered several classes of nitro-containing epoxycompounds which are capable of polymerization to the correspondingpolyalkylene ether polyols and then to polyurethane propellant binders.These new compounds enable propellant chemists to prepare propellantbinders which are characterized by the benefits associated with thepresence of a multiplicity of ether linkages along the polymer chain,and at the same time retain the energy and oxidizing power of nitrogroups.

It is, therefore, an object of this invention to prepare several novelclasses of nitro-containing epoxy compounds capable of undergoingpolymerization to high molecular weight polyalkylene ether diolscontaining many nitro groups. Another object of our invention is toprepare these new epoxy compounds in a manner whereby they are obtainedin the high purity required to meet the exacting standards demanded bythe reliability requirements Which exist in the solid propellant art.These objects, as well as others, will be evident from the more specificdescription of our invention which follows.

The novel epoxy compounds of this invention are those having thefollowing generic formulae:

wherein R is lower alkyl, preferably of from 1 to about 6 carbons suchas methyl, ethyl and hexyl;

wherein R is lower alkyl of from 1 to about 6 carbons;

and

(III) NO:

wherein R is lower alkyl of from 1 to about 6 carbons.

In each of the foregoing three formulae, R R or R is most preferablymethyl or ethyl.

Compounds within the scope of Formula I include:

5 ,S-dinitro-1,2-epoxyhexane 5,5-dinit'ro-1,2-epoxyheptane 5 ,5-dinitro-1,2-epoxyoctane 5,5-dinitro-1,2-epoxydecane 5,5-dinitro-1,2-epoxydodecane Illustrative compounds of the type defined byFormula II include:

5, 5-dinitro-2,3 -epoxyhexane 5 ,5 -dinitro-2,3-epoxyheptane 5 ,5-dinitro-2,3 -ep oxyoctane 5 ,5 -dinitro-2,3 -epoxydecane 5 ,5-dinitro-2,3 -epoxydodecane Preferred species of the Formula IIIcompounds are:

4-nitraza-2,3 -ep oxypentane; 4-nitr'aza-1,2-epoxyhexane; 4-nitraza- 1,2-epoxyo ctane; 4-nitraza-1,2-epoxydecane; 4-nitraza-1,2-epoxydodecane.

The compounds of Formula I are prepared in accordance with the followinggeneral reaction equation:

wherein R is as defined above; X is halogen, such as iodine, bromine orchlorine; and M is an alkali or alkaline earth metal such as lithium,sodium, potassium, cal cium or barium, and p is one or two and is equalto the valence of M This reaction is carried out in the presence of alower alkanol such as methanol or ethanol. While not critical, the M(OH) reactant is usually employed in about a stoichiometric amount or aslight excess. The reaction takes place satisfactorily at roomtemperature, however, any temperature from about 0 C. to about C. issuitable. The 5,5-dinitro-l-halo-Z-alkanol starting materials utilizedin this reaction are readily obtained by treating the corresponding5,5-dinitro-1,2-alkanediol with a dehydrating acid such as sulfuric acidin the presence of a hydrogen halide.

The following example illustrates the preparation of a compound of thetype depicted in Formula I.

The examples of our specification are presented solely to illustrate theinvention, and should not be regarded as limitative in any way. In theexamples, the parts are by weight unless otherwise indicated.

EXAMPLE I 5 ,5 -dinitr0-1 ,Z-epoxyhexane 14.3 grams (0.0686 mole) of5,5-dinitro-1,2-hexanediol was added to a mixture of 2.5 grams (0.150mole) of 48 percent aqueous hydrobromic acid and 3.5 ml. (0.0642 mole)of concentrated sulfuric acid. The reaction mixture was refluxed (liquidtemperature 128 C.) for one hour. The reflux condenser was then removedand the unreacted hydrobromic acid was driven off by boiling for anadditional one-half hour. Two layers were present in the reactionmixture, the top water layer and a thick, dark organic layer.Twenty-five milliliters of methylene chloride was added in order tolower the viscosity of the organic material and to facilitate itsremoval from the vessel. The layers were then separated and the organiclayer was extracted times with a total of 100 ml. of water to removeresidual sulfuric acid, hydrobromic acid and unreacted5,5-dinitro-1,2-hexanediol. After the bulk of the methylene chloride wasremoved from the oil layer by partial vacuum distillation, the remainderof the liquid was allowed to stand at room temperature at a pressure ofapproximately 1 10- mm. for approximately onehalf hour to insure theremoval of water and methylene chloride. No condensate was obtained atthis pressure as the temperature was raised until a vapor temperature145 to 150 C. was reached, at which point 7.2 grams of a clear, ambercolored, viscous distillate was obtained. Analysis of this material bytitration of a weighed sample with standard methanolic sodium hydroxideto the phenolphthalein end point indicated the purity of the 5,5-dinitro-l-bromohexanol-Z to be 98.23 percent.

A portion of this bromohydrin was titrated with methanolic sodiumhydroxide solution (approximately 0.2 N) to the phenolphthalein endpoint. The methanol was then removed at reduced pressure leaving an oiland a white precipitate (NaBr). The oil was decanted off and distilled(B. 110 C. at approximately 1 l0 mm.). Titration of this distillate forepoxide oxygen by treatment with an excess of standard HCl (0.2 N) indioxane and back titration with 0.1 N methanolic sodium hydroxide to acresol red end point indicated that a purity of 92.4 percent wasobtained, calculated as 5,5-dinitro-l,2-epoxyhexane.

The compounds of Formula II are prepared according to the followingreaction scheme:

wherein R is as defined above, and Y is a monovalent aromatic oraliphatic organic radical. Typically, Y is lower alkyl, lower haloalkylsuch as trifluoromethyl, or phenyl. The per-acids used in this reactionand in preparation of the compounds of Formula III, below, are preparedby treating the corresponding acid anhydride with hydrogen peroxide at20 C. to about +20 C. Suitable per-acids for use in this reactioninclude peroxytrifluoroaceti-c acid, peroxyacetic acid and peroxybenzoicacid. The 5,5-dinitro-2-alkenes used in the reaction are produced bydehydrating the corresponding 5,5-dinitro- 2-alkanols with sulfuric acidat elevated temperature. The 5,5-dinitro-2-alkene and the per-acid areutilized in about stoichiometrically equivalent amounts, or astoichiometric excess of the per-acid. Preferably, the reaction iscarried out in a solvent for the alkene reactant such as thehalohydrocarbons (methyl chloride, methylene dichloride, methyl bromide,etc.). Best yields result when there is added to the reaction media abuffer compound. Common buffers which are of benefit include sodiumcarbonate, disodium acid phosphate, and sodium bicarbonate. The reactionnormally takes place at a temperature of from about 20 C. to about 150C.

The following shows the preparation of a Formula II compound.

EXAMPLE 1r 5,5-dz'nz'tr0-2,3-ep0xyhexane 45.34 ml. of 90 percenthydrogen peroxide was added to 215.5 ml. of anhydrous methylene chlorideand this two phase system was cooled to 0 C. 273.6 ml. oftrifluoroacetic anhydride was then added over a period of 1 /2 hours,during which time the reaction mixture became a one phase, homogeneoussolution. Titration of an aliquot of this reaction mixture with KINa S Oin acetic acid indicated no appreciable loss of peroxide oxygen in thisreaction.

The above reaction mixture, containing both peroxytrifluoroacetic acidand trifluoroacetic acid, was then added over a 2% hour period to awell-stirred, refluxing mixture of 800 ml. of methylene chloridecontaining 150 grams of 5,5-dinitro-2-hexene and 292.3 grams of sodiumacid carbonate. The olefin was miscible with the methylene chloride.After addition was completed, the reaction mixture was refluxed for anadditional half hour.

The inorganic salts were then dissolved by the addition of 1500 ml. ofwater to the reaction mixture. The layers were separated and the waterlayer extracted three times with a total of 650 ml. of methylenechloride. The methylene chloride layers were then dried over magnesiumsulfate, filtered, and the solvent removed at reduced pressure. A highboiling liquid remained which was analyzed for epoxide oxygen by theaddition of excess standard I-ICl in dioxane (10 ml. of 0.2 N acid per0.2 g. sample) then back titration of unreacted acid with standard (0.2N) methanolic sodium hydroxide to the cresol red end point. The solutionanalyzed 84.3 percent pure, calculated as 5,5-dinitro-2,3-epoxyhexane,indicating a crude yield of 84.7 percent had been attained.

A portion of this solution was extracted with water, dried overmagnesium sulfate and distilled in a bulb tube yielding a center-cut(B.P. C. at approx. IX 10' mm.) which analyzed 96.9 percent pure. Anelemental analysis of this material gave the following results.

Calculated: C, 37.90; H, 5.31; N, 14.70. Found: C, 37.87; H, 5.16; N,14.20.

The product is a clear, pale yellow, mobile liquid, sp. gr. 1,269, N1.4569.

The compounds of Formula III result from the reaction shown in thefollowing equation:

wherein R is as defined previously, and Y is a monovalent aromatic oraliphatic organic radical such as phenyl, trifiuoromethyl, methyl, etc.

The above reaction is preferably, although not necessarily carried outin the presence of a halohydrocarbon solvent of the type employed in thepreparation of the compounds of Formula II. In this reaction,proportions are not critical, but best results are obtained when theper-acid is used in a slight stoichiometric excess over the amount ofthe olefin reactant. The reaction temperature usually is within therange from about 0 C. to about C. Common buffers, such as sodiumcarbonate, disodium acid phosphate and sodium bicarbonate are preferablyemployed in the reaction mixture and their presence is found to resultin higher product yields.

The following two examples illustrate the preparation of the compoundsof Formula III.

EXAMPLE III 4-nitraza-1,Z-epoxypenlane Twenty-nine grams (0.25 mole)4-nitraza-l-pentane Was added to a solution of 38 grams (0.275 mole)perbenzoic acid in chloroform (.06693 grams/ml.), and the resultingsolution was stored overnight in a refrigerator. After 18 hours, only13.5 percent of the theoretical amount of perbenzoic acid had beenconsumed, and the solution was stored at ambient temperature in the darkfor the remaining reaction period. At the higher temperature, the rateof epoxidation was increased, but the increased rate of decomposition ofthe perbenzoic acid was more pronounced. After 47 hours, 37.5 percent ofthe theoretical amount of perbenzoic acid was consumed. Sufficientperbenzoic acid was added at this time to give a 106 mole percent excessof this reagent over the remaining quantity of the olefin, and thereaction was continned for a total period of 136 hours. The solution wastreated with sodium carbonate solution until the chloroform solutionfailed to give a test for perbenzoic acid, washed with water, and driedover anhydrous calcium sulfate. Distillation of the solvent at reducedpressure gave 27.9 grams residue, n 1.5046. On prolonged storage in thecold, this liquid deposited 1.3 grams crystals which were purified byrecrystallization from methanol and shown to be benzoyl peroxide,apparently carried through from the preparation of perbenzoic acid. Thefiltrate was transferred to a small Claisen flask and distilled atreduced pressure.

Cut 1: B.P. 63 C./l0 4.1 gram; n 1.4880 Cut 2: B.P. 63.5 C./810/L; 11.8;11 1.4868 Cut 3: B.P. 635-67 C./8,u; 1.7 gram. Residue: 7.4 grams.

The residue set to a glass on cooling to room temperature and was thehydroxybenzoate resulting from the ring opening of the epoxide. Thefirst two fraction corresponded to a 60.2 percent yield of crude4-nitraza-1,2- epoxypentane. These fractions were combined andredistilled.

Cut 1: B.P. 53-57 C./ 3-4,u; 1.9 grams; n 1.4876 Cut 2: B.P. 53-57"C./34/.L; 9.1 grams; 11 1.4-870 Cut 3: B.P. 53-57 C./4,u.; 2.3 grams; 111.4867

The infrared spectrum of the second fraction (3.45 (w.),

5.85(W.), 6.60(s.), 6.80(m.), 6.90(m.), 7.10(m.), 7.50(s.), 7.75(v.s.),9.85(m.), 10.40(m.), 10.65(m.), 10.95(W.), 1l.70(rn.), 12.00(W.),l3.10(m.), 15.10(W.))

EXAMPLE IV 4-niiraza-1 ,Z-epoxypentane Peroxytrifluoroacetic acid wasprepared by the addition of 42.3 ml. (0.3 mole) trifiuoroaceticanhydride to a stirred suspension of 7 ml. (0.25 mole) 90 percenthydrogen peroxide in 50 ml. dry methylene chloride, with icebath coolingduring a 10 minute period. The reaction solution was stirred in the coldfor an additional minutes, transferred to a separatory funnel, and addedto a vigorously agitated mixture of 24.4 grams (0.21 mole)4-nitraza-1-pentene, 95.4 grams (0.9 mole) powdered sodium carbonate,and 200 ml. methylene chloride during a 35 minute period. The mixturewas held at 30-35 C. by external cooling during this addition, and wasthen heated at reflux temperature with continued stirring for 30minutes. Ice water (500 ml.) was added, and the mixture was allowed tostir until dissolution of the inorganic salts. The two-phase mixture wasseparated, and the aqueous phase was extracted four times With 50 ml.portions of methylene chloride. The combined organic phases were driedover anhydrous calcium sulfate, and the solvent was distilled atdiminished pressure. The reduced pressure distillation of the residuefrom a Claisen flask did not give an eflicient separation of product andstarting material (total distillate, 20.4 grams n 1.4724 to 1.4811;residue 1.3 grams n 1.4884), and the distillate was fractionated using aHolzman column.

Cut 1: B.P. 5658 C./2 mm.; 4.9 grams; n 1.4745 Cut 2: B.P. 56-96 C./2mm.; 2.8 grams; 11 1.4747 Cut 3: B.P. 96 C./2 mm.; 9.7 grams; 31 1.4832Residue: 1.4 grams; n 1.4832

The first two fractions represent a 31.6 percent recovery of4-nitraza-1-pentene and the third cut corresponds to a 35 percent yieldof 4-'nitraza-1,2-epoxypentane.

As can be seen from these examples, the reactions of our invention aregenerally carried out at atmospheric pressure. The products are isolatedin conventional manner by distillation, evaporation, crystallizationand/or extraction.

The nitro-containing epoxy compounds of this invention are converted tohigh molecular weight polyether diols by polymerization at roomtemperature or at elevated temperature in the presence of water orethylene glycol. The resultant diols have a molecular weight of from1,000 to about 10,000, and are readily polymerizable withpolyisocyanates, such as toluene diisocyanate or 3-nitraza-1,5-pentanediisocyanate, to yield polyurethane polymers. These polyurethanepolymers are of high specific impulse, and provide solid rocketpropellants of improved mechanical and chemical properties. Thus, as isindicated above, the epoxy compounds of this invention enable thoseskilled in the art to prepare a new class of improved solid propellants.

The epoxy compounds of this invention, which contain one or more nitrogroups, are also inherently useful as high explosives. In addition,these compounds can be used in any conventional explosive missile,projectile, rocket, or the like, as the main explosive charge. Anexample of such a missile is described in US. Patent 2,470,- 162, issuedMay 17, 1949. One way of using such high explosives in a device such asthat disclosed in US. Patent 2,470,162 is to absorb the liquid explosivein an absorbent material such as cellulose, wood pulp, or sawdust. Theresultant dynamite-type explosive can then be packed into the warhead ofthe missile. A charge thus prepared is sufficiently insensitive toWithstand the shock entailed in the ejection of a shell from a gunbarrel or a rocket launching tube under the pressure developed fromignition of a propellant charge, and can be caused to explode onoperation of an impact or time-fuse mechanism firing a detonatingexplosive such as lead azide or mercury fulminate.

Having fully described the invention, it is intended that it be limitedonly by the lawful scope of the appended claims.

We claim:

1. Compounds of the formula:

wherein R is lower alkyl.

2. The compound 5,5-dinitro-1,2-epoxyhexane. 3. Compounds of theformula:

wherein R is lower alkyl.

4. The compound 5,5-dinitro-2,3-epoxyhexane.

References Cited UNITED STATES PATENTS 3,211,792 10/1965 Osbond et al260570.6

FOREIGN PATENTS 8/1958 Germany.

WALTER A. MODANCE, Primary Examiner.

NORMA S. MILESTONE, Examiner.

1. COMPOUNDS OF THE FORMULA: